Preparation of sulfonated alkyl aryl detergent slurries



J. J. MORRISROE PREPARATION OF' SULFONATED ALKYL ARYL DETERGENT SLURRIES Filed Dec. 24, 1951 March 8, 1955 United States Patent O PREPARATION F SULFONATED ALKYL ARYL DETERGENT SLURRIES Iohn J. Morrisroe, San Marino, Calif., assignor to Purex Corporation, Ltd., South Gate, Calif., a corporation of California tion of detergent slurry stocks and ultimately'commercial detergent and washing compounds containing as an active constituent one or a mixture of the petroleum-v derived alkyl aryl sulfonates having the general formula R-SOz-DI-l, wherein R is any benzenoid hydrocarbon radical having two or more replaceable nuclear hydrogen atoms and at least one nuclear hydrogen atom replaced by an aliphatic or alicyclic radical containing 8 to 1S carbon atoms. These aryl substituted alkanes are more fully described in theA United States Lewis Patents No. 2,477,382 and No. 2,477,383. Specific examples are dodecyl, tridecyl, tetradecyl and pentadecyl benzene sulfonic acid. Contemplated generally as the active detergent constituent are the alkyl aryl sulfonates in which the alkyl radical contains between 8 to 18 carbon atoms and is derived from aliphatic or alicyclic compounds of either straight or branched, symmetrical or near symmetrical structure.

The particular objects and important signitcances of the invention may best be appreciated by first referring briefly to the general nature and development of the synthetic detergent art, with particular reference to the sources and preparation of the so-called actives, i. e. organic sulfates and sulfonates. The principal material first used in making synthetic detergents was commercial lauryl alcohol. The total consumption of synthetic detergents was relatively low until the introduction of the heavy duty type characterized by the addition of large amounts of phosphate to the active ingredient. There arose no serious problems of concentration of the lauryl sulfate form, by the reaction of the lauryl alcohol with sulfuric acid, because the amount of acid needed in excess of the theoretical amount required for the sulfonation, was not large, and the amount of lsodium sulfate formed along with, the lauryl sulfate did not preclude the use of large amounts of phosphate.

Because of lower cost, greater stability and higher performance in certain combinations, there has come into increasing use the petroleum derived alkyl aryl sulfonates, such as the alkyl benzene sulfonates obtained from polypropylene as described in the above mentioned Lewis patents. These polypropylbenzenes require around 260 to 350% of the theoretical amount of acid to eect sulfonation by conventional methods. Formation of the alkyl benzene sulfonate is accompanied with such large amounts of sodium sulfate as to require separation of the sulfate before the alkyl benzene sulfonate can be compounded with phosphates to make heavy duty synthetic detergent. Known methods that might be suggested for making a concentrated alkyl benzene sulfonate include the following: Separation of the excess sulfuric acid from the sulfonic acid by addition of Water, followed by settling; separation of sodium sulfate liquor after neutralization by addition of water and settling; sulfonation with less acid followed by removal of unreacted alkyl benzene with a solvent; and sulfonation with sulfur trioxide.

Such methods have been tried and are workable to a degree, but they are characterized by certain limitations which are distinct impediments to the production of high volumes of lower cost heavy duty detergents. In the acid separation method, the temperatures must be kept high with the result that the sulfonic acid is discolored and degraded. This degradation requires extensive bleaching to make a commercial product.

water to dilute the acid, and the use of large amounts ice of bleach, require corrosion-proof equipment resistant to both strong and weak acids.

Separation of sodium sulfate liquor after neutralization required a large number of' tanks orv centrifuges, because of the variable nature of the settling that occurs. There is a loss of the valuable active ingredient in a sodium sulfate liquor that is removed by settling. The viscosity of the slurry and the tendency of the alkyl benzene sulfonate to form a gel are among the principal causes of the variable results in centrifuging or settling.

Processes in which lower degrees of sulfonation are accepted with dependence upon an extract solvent require large and extensiveadditions to plant investment. The solvent system must operate under corrosive conditions and the materials of construction are costly.

While sulfur trioxide sulfonation in sulfur dioxide readily yields concentrated active, the properties of free sulfur trioxide make its use hazardous and inconvenient. lt must be stabilized with substances such as boric anhydride to prevent formation of unstable polymers. Handling of sulfur trioxide differs from the handling of oleum to the extent that any contamination with excess moisture nullifies the degree of stabilization, resulting in a melting point higher than the normal 62-63 F. The relatively narrow temperature range between the normal melting point (62-63 F.) and boiling point (113 F.) requires that provisions be made to protect the material from extremes of temperature while in storage and during transfer. Thus sulfur trioxide should be stored at 90 F. and temperature in the order of 113 lf". avoided because of vapor pressure build up that could possibly rupture the container.

There are three forms of sulfur trioxide, namely the alpha, beta., and gamma. The gamma form is produced on distillation, but polymerizes at low temperatures to a mixture of alpha and beta. The alpha form is the most stable, but is capable of explosion on melting because on melting it abruptly converts to the gamma form having high vapor pressure as compared to the vapor pressure of solid alpha sulfur trioxide. The increase can be as much as six atmospheres.

Heretofore it has been proposed to make detergent stocks by the sulfonation of certain aromatics with oleum while the aromatic is dissolved in sulfur dioxide. Typically, t has been proposed to sulfonate an alkylated diphenyl with 65% oleum in sulfur dioxide. However, insofar as I am aware, all such proposals have failed to recognize or take advantage of the critical nature of the mol ratio of acid to alkane discovered in accordance with the present invention to be of essential importance in the production of a concentrated slurry of the petroleum derived alkyl aryl sulfonates herein contemplated, and the essential requirements for the direct production of the sulfonated alkane in substantially anhydrous condition, followed by its conversion to a concentrated neutralized slurry. Prior proposals further have failed to take into account the importance of being able to obtain directly and in a concentrated slurry, a high ratio of the neutralized or alkali metal sulfonate to sodium sulfate in the manufacture of a heavy duty detergent from the present class of alkanes.

It has been found that by'sulfonating the poly propyl benzenes using fuming sulfuric acid in such proportions as to afford a mol ratio of sulfur trioxide to the alkane The use of so within certain critical ranges, it is -possible to produce a concentrated slurry having the particular qualities and composition required for heavy duty detergency. In carrying out the sulfonation of the alkane mixed with sulfur dioxide and fuming sulfuric acid, it is found that a mol ratio of 1.5 to 2.0 mols of 65% fuming oleum per mol of alkane or equivalent fuming acid giving 1.0 to 1.3 mols of free sulfur trioxide to 1.0 mol (average mol weight) of alkane is required to produce a sulfonic acid which on neutralization yields a sulfonate having suiciently low unsulfonated oil and sodium sulfate content to be capable of formulation directly into a heavy duty detergent. A mol of fuming sulfuric acid is defined as that quantity which contains one atomic weight of chemically combined sulfur. The preferred ratio is 1 .7 mols of 65% fuming oleum or equivalent fuming acid giving a sulfur trioxide to alkane mol ratio of about 1.1. It is further found desirable to employ oleum containing` about 60 to 75% free sulfur trioxide, with the preferred concentration being 65 to 70%. The specific mol ratio-appears to be critical in using for example 60 to 65% oleum, in that any considerable reduction in the mol ratio results in a sharp rise in unsulfonated oil, and on the other hand,

a considerable increase in the mol ratio produces a sulfonate containing too much sodium sulfate to be used in a heavy duty product, wherein it is .desirable that the ratio of percent active to percent sodium sulfate be not less than about 3.7 to 1.0. l

It may be observed that sulfonation directly with 60 to 75% oleum is not feasible since acid of this strength severely chars and degrades the alkane. By diluting the oleum with liquid sulfur dioxide as a solvent, the action of the former can be made less vigorous and the reaction is readily controllable. Where sulfur dioxide is used both as a diluent and the only refrigerant, sufficient sulfur dioxide must be used to absorb the heat of the sulfonation reaction. Under this condition it is preferred to conduct the sulfonation using a weight proportion of sulfur dioxide to alkane of about 2 to 4, at a temperature between about 20 to 65 F.

The various features of the invention discussed in thev foregoing, as well as additional important objects, will be understood most readily and to best advantage from the following description of a typical procedure for carrying out the invention, and as illustrated by the accompanying ow sheet drawing.

Oleum containing say 60 to 75% sulfur trioxide is taken from storage through line 11 and pump 12 int o a weigh tank 13 for agitated admixture with sulfur dioxide supplied from its storage 14 through line 15. A s previously indicated, the quantity of liquid sulfur d1- oxide added to a given quantity of the oleum will be such as to give a weight ratio of about 2 to 4 parts of sulfur dioxide to the alkane subsequently added. After thorough agitation in the weigh tank, a batch of theoleum and sulfur dioxide mixture is discharged through lines 16 and 17 leading to the sulfonator generally indicated at 18.

The alkane comprising typically mono substituted alkyl benzene containing poly propyl side chains and having an average molecular weight of about 250, 1s taken from storage 19 through line 20 and pump 21 to the weigh tank 22 from which a batch, quantitatively determined in proper weight ratio to the oleum and sulfur dioxide, is discharged by the pump through lines 23 and 24. As previously indicated, for reaction in the sulfonator, the oleum and alkane are proportioned to give a mol ratio of free sulfur trioxide to alkane within the range of about 1.0-1.3 to 1.0; the preferred ratio being about 1.1 to 1.0.

The sulfonator 18 may be of any suitable type of construction, and is shown typically to comprise a corrosion resistant tank 25 into which the ow of the mixture from line 17, or lines 17 and 241, is regulated by a valve 26 (controlled by an operative connection 27 with the thermostat 28), in accordance with the temperature of the reactants in the sulfonator, and which as previously indicated, may range between 2O to 65 F.

The system may be adapted for either or both continuous or batch sulfonation, depending upon the way in which the reactants are fed to the sulfonator 18. For batch operation, the pre-weighed alkane charge is delivered from the alkane weigh tank to the sulfonator by way of lines 24 and 17. Then the admixed oleum and sulfur dioxide are fed to the sulfonator through line 17 at a controlled rate which will permit progressive sulfonation of the alkane charge, preferably while the latter is agitated, at a rate which will avoid overheating. Alternately, and for continuous sulfonation, the alkane derived dioxide. Such heating is accomplished typically by maintaining a continuous circulation of heated oil from storage 30 through line 31 and pump 32 to the coil 33 in the sulfrom the bulk source 19, may be pumped continuously v and at a controlled rate through lines 24 and 241 into the sulfonator while simultaneously the oleum and sulfur dioxide mixture is pumped continuously and in the specified reacting proportion in relation to the alkane separately through line 17 to the sulfonator. The resulting mixture is maintained in the sulfonator for a period of time sucient for the reaction to go to completion, and the sulfonate is continuously withdrawn through line 62.

An important feature of the invention, and one relating to the capacity of the process for producing directly a substantially anhydrous and concentrated sulfonate neutralizable to a concentrated slurry, is the provision of means for supplying heat to the produce after sulfonation to assist in substantially complete removal of the sulfur fonator after addition of the acid is completed. Leaving the coil, the oil returns to the storage 30 through line 34. The storage oil is shown to be continuously heated by circulation through line 35, pump 36, heater 37 and the return line 38, the heater being supplied with steam from line 39 communicating through the heater with the trap outlet 40 and the steam flow to the heater being regulated by thermostat 41 and an operative control 42 to maintain a. uniform oil storage temperature.

Heat of course is developed in the sulfonator 18 by reason of the exothermic sulfonation reaction. The mixture however continuously loses heat and at a rate suicient to maintain the sulfonation temperature within the indicated range, by the continuous vaporization and release of sulfur dioxide through line 44 leading to the knock out pot or trap 45 through which any separated liquid materials drain back to the sulfonator through line 46. From the knockout pot 45, the sulfur dioxide gas flows through line 46 to an appropriate and diagrammatically indicated scrubber 47 wherein the gas is contacted with 93-l00% sulfuric acid being continuously circulated from its storage 48 through line 49, pump 50 and in direct contact with the sulfur dioxide in the scrubber. Prom the scrubber, the acid is returned to storage through line 51, cooler 52, line 53 and pump 541. Leaving the scrubber, the sulfur dioxide gas passes through line 54, sulfuric acid trap 55 and line 56 to one or more compressors 57 which liquefy the gas wholly or in part. From the fur dioxide is returned through line condenser 59 to the storage 14.

Ordinarily it may be desirable to introduce a portion of the sulfur dioxide from storage 14 directly into the sulfonator, as for the purpose of more effective cooling and temperature control of the sulfonation zone. Accordingly, having mixed with the oleum a portion (say 80%) of the total liquid sulfur dioxide sufficient for the desired dilution of the oleum, the remaining portion may be introduced directly from storage to the sulfonator, as through line 60 past an appropriate pressure reduction control 61. As will be understood, ultimately, during the course of as complete as possible sulfonation of the alkane, all but a small portion of the sulfur dioxide diluent will become vaporized from the sulfonator to the recovery system.

As the drawing shows, provision may be made for employing plural sulfonators, as for alternate batch operation, for reacting the weighed quantities of oleum and alkane, and for employing common facilities for recovering the sulfur dioxide and product sulfonic acid. Assuming typically two corresponding sulfonators to be used, and that sulfonator 18 is to be taken off stream, the reactant feed may occur as explained before, through lines 171 and 241e to a second sulfonator 181 .containing a heating coil 331 having line connections 311 and 341 with the heated oil supply and return lines 31 and 34. The sulfonator 181 may also be connected through line 601 with the reduced pressure sulfur dioxide line 60. As before, sulfur dioxide released from the sulfonator passes through line 441 to the knockout pot 451 having its drain connection 461 with the sulfonator, the sulfur dioxide gas released through line 461 passing through the scrubber 471 (corresponding to scrubber 47), and thence through line 541, trap 551 and line 561 to the compressors for return to the storage 14.

Upon completion of the sulfonation, the resulting sulfonic acid mixture is withdrawn from the sulfonators through line 62 for discharge by pump 63 through line 64 to appropriate equipment for storage, further treatment and neutralization. In order that the sulfonic acid mixture may be completely freed from any residual sulfur dioxide, it is preferred to subiect the mixture to treatment under such temperature and low pressure conditions as will assure final expulsion of the sulfur dioxide. Accordingly, the sulfonic acid stream is shown to be pumped through line 64 to an appropriate chamber 80 in which is maintained a pressure between about 0.1 to 20 inches of mercury (absolute), and from which the vacuum is drawn through line 81. The temperature in chamber 80 preferably is maintained in a range of about 20 to 70 F. To give extended surface exposure to the acid mixture, the stream may be sprayed into chamber 80 with resultant effective freeing of the sulfur dioxide which is taken compressors the sul- 58 and water-cooled snospss E througli the vacuum line 81. From the vacuum chamber the sulfur-dioxide-free sulfonic acid stream is taken through line 82 to storage.

As to neutralization, it will be understood that the anhydrous and concentrated vacuum-treated sulfonic acids may be given any suitable neutralization roductive of a concentrated detergent slurry. Typi y the sulfonic acids maybe reacted with a 20 to 25% aqueous solution of an alkali metal hydroxide! preferably sodium hydroxide, the alkali being used in quantity just sufficient to completely neutralize the acid to convert all the acid to alkali metal sulfonate. Typically, I may employ for production of a concentrated slurry, the vacuum neutralization methods and apparatus disclosed in the Alan C. Stoneman application Serial No. 167,642 on Vacuum Neutralization of Detergents, led June 12, 1950, now Pat. No. 2,613,218. The resulting slurry is composed principally of the so-called active, i. e. alkali metal sulfonate, alkali metal sulfate and perhaps some unreacted oil derived initially from the alkane. Minor amounts of alkali metal sulite may be present.

In accordance with the invention as described, it is readily possible to produce a concentrated slurry having the following composition; the percentages being calculated on an anhydrous basis: Active-70 to 80%, alkali metal sulfate-under 20% (typically between about 18 to 19.5%), and an oily component extractable in petroleum ether-under about 2.5%. It is contemplated that the weight ratio of active, i. e., alkali metal alkyl aryl sulfonate, to the alkali metal sulfate, e. g. sodium sulfonate to sodium sulfate, shall not be less than 3.7 to 1.0. A further property of the slurry having considerable importance by reason of the commercial color requirements for detergents, is the light and substantially white slurry color indicative of the absence of appreciable overl sulfonation in the production of the sulfonate. As measured in reilectance units (as by the commonly used Photovolt Corporation retiectometer), the color of the product may be kept in excess of 74 and as high as 90 units.

The following examples are given of typical materials and conditions employed for production of the sulfonic acids, and of the properties of the slurry resulting from neutralization of the sulfonic acids. The slurry composition is stated on an anhydrous basis.

Example 1 Alkane lbs-- 5.0 60% oleum (113.7% HzSOi) lbs-- 2.94 SO2 added to oleum lbs-- 20 Acid addition time minutes-- 24 Digestion time hours 3% Approximate sulfonation temp 20-30 Slurry color rellectance units-- 80 Per cent active 70.8 Per cent sodium sulfate 18.4 Per cent oil soluble in petroleum ether 1.6 Ratio: active/NaaSOi 3.85

Example 2 Alkane lbs-- 5.0 60% oleum (113.7% HzSOi) lbs-- 2.94 lbs-- 2l minutes-- l5 Approximate sulfonation temp 50-55 Digestion time hours-- 4 Slurry color retiectance units-- 75 Percent active 73.2 Per cent sodium sulfate 18.1 Per cent oil soluble in petroleum ether 0.8 Ratio: active/NazSOi 4.04 Example 3 Alkane lbs-- 10 72% oleum (116.3% HzSO4.).. lbs-.. 5.73 SO2 added to oleum 1bs 40 Acid addition time ininutes..- 19 .Digestion time hours-- 3 Approximate sulfonation temp F 50-60 Slurry color reflectance units-- 77.5 Percent active.' 70.8 Percent sodium sulfate 18.8 Percent oil soluble in petroleum ether 1.4 Ratio: active/NarSOi 3.77

Where in the examples given above the active/NaaSOs ratio isindicated to exceed the theoretical the reason is that the boiling sulfur dioxide may remove some of the acid as vapor or mist, and therefore produce a lovlverl sodium sulfate content on neutralization.

c aim:

1. The method of producing a sulfonated detergent slurry, that includes reacting a petroleum-derived aryl substituted alkane material having alkyl radicals containing from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of sulfuric acid containing betweenJ about 60 to 75% free sulfur trioxide, the mol ratio of free sulfur trioxide to the alkane material being between about 1.0 to 1 .3 mols of sulfur trioxide to 1.0 mol of alkane, separating sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and neutralizing the anhydrous stock so formed to produce a concentrated slurry.

2. The method of producing al sulfonated detergent slurry, that includes reacting a petroleum-derived aryl substituted alkane'material having alkyl radicals containing 'from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of sulfuric acid containing free sulfur trioxide, the mol ratio of free sulfur trioxide to the alkane material being between about 1.0 to 1.3 mols of sulfur trioxide to 1.0 mol of alkane, separating the sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and neutralizing the anhydrous stock so formed to produce a concentrated slurry.

3. The method of producing a sulfonated detergent slurry, that includes reacting a petroleum-derived aryl 'substituted alkane material having alkyl radicals containing from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of sulfuric acid containing between about 60 to 75% free sulfur trioxide, the mol ratio of sulfur trioxide to the alkane material being between about 1.0 to 1.3 mols of sulfur trioxide to 1.0 mol of alkane, separating the sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and neutralizing the anhydrous stock so formed with alkali metal hydroxide to produce a concentrated slurry containing on an anhydrous and weight basis between about 70 to 80% alkali metal sulfonate, under about 20% alkali metal sitiklfate, and under about 2.5% oil soluble in petroleum e er.

4. The method of producing a sulfonated detergent slurry, that includes reacting a petroleum-derived aryl substituted alkane material having alkyl radicals containing from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of sulfuric acid containing free sulfur trioxide, the mol ratio of sulfur trioxide to the alkane material being between about 1.0 to 1.3 mols of sulfur trioxide to 1.0 mol of alkane, separating the sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and neutralizing the anhydrous stock so formed with alkali metal hydroxide to produce a concentrated slurry containing on an anhydrous and weight basis an alkali metal sulfonate to alkali metal sulfate ratio not less than 3.7 to 1.0.

5. The method of producing a sulfonated detergent i slurry, that includes reacting a petroleum-derived aryl substituted alkane material having alkyl radicals containing from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of sulfuric acid containing free sulfur trioxide, the mol ratio of sulfur trioxide to the alkane material being between about 1.0 to 1.3 mols of sulfur trioxide to 1.0 mol of alkane, separating sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and neutralizing the anhydrous stock so formed with alkali metal hydroxide to produce a concentrated slurry containing on an anhydrous and weight basis between about 70% to 80% alkali metal sulfonate, under about 20% alkali metal sulfate, and under about 2.5% oil soluble in petroleum ether.

6. The method of producing a sulfonated detergent slurry, that includes reacting a petroleum-derived aryl substituted alkane material having alkyl radicals containing from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of free sulfur trioxide, the mol ratio of the sulfur trioxide to the alkane material being between about 1.0 to 1.3 mols of sulfur trioxide to 1.0 mol of alkane, separating sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and neutralizing the anhydrous stock so formed with alkali metal hydroxide to produce a concentrated slurry containing on an anhydrous and weight basis between about 70% to 80% alkali metal sulfonate, under about 20% alkali metal sulfate, and under about 2.5% oil soluble in petroleum ether.

7. The method of producing a sulfonated detergent slurry, that includes reacting a petroleum-derived aryl substituted alkane material having alkyl radicals containing from 8 to 18 carbon atoms with an anhydrous solution in sulfur dioxide of free sulfur trioxide, the mol ratio of the sulfur trioxide to the alkane material being between about 1.0 to 1.3 mols of sulfur troxide to 1.0 mol of alkane, separating sulfur dioxide from the resulting substantially anhydrous sulfonic acid stock, and nally neutralizing the anhydrous stock so formed with alkali metal hydroxide to produce a concentrated slurry containing on an anhydrous and weight basis an alkali metal sulfonate to alkali metal sulfate ratio not leas than about 3.7 to 1.0.

References Cited in the le of this patent Bloch et al. N 

1. THE METHOD OF PRODUCING A SULFONATED DETERGENT SLURRY, THAT INCLUDES REACTING A PETROLEUM-DERIVED ARYL SUBSTITUTED ALKANE MATERIAL HAVING ALKYL RADICALS CONTAINING FROM 8 TO 18 CARBON ATOMS WITH AN ANHYDROUS SOLUTION IN SULFUR DIOXIDE OF SULFUR TRIOXIDE, THE MOL RATIO OF ABOUT 60 TO 75% FREE SULFUR TRIOXIDE, THE MOL RATIO OF FREE SULFUR TRIOXIDE TO THE ALKANE MATERIAL BEING BETWEEN ABOUT 1.0 TO 1.3 MOS OF SULFUR TRIOXIDE TO 1.0 MOL OF ALKANE, SEPARATING SULFUR DIOXIDE FROM THE RESULTING SUBSTANTIALLY ANHYDROUS ACID STOCK, AND NEUTRALIZING THE ANHYDROUS STOCK SO FORMED TO PRODUCE A CONCENTRATED SLURRY. 